1. Field of the Invention
The present invention relates to medical instruments and more particularly to an EEG (electroencephalograph) instrument having a microprocessor based digital analysis system for screening a large population (mass) for brain disorders.
2. Related Art
At the present time a limited number of specialists in human brain disorders, such as neurologists and psychiatrists, have an EEG (electroencephalograph) in their office. Such office EEG machines typically are 2 to 8 channel instruments having 2 to 8 electrode leads which are placed on the scalp, a preamplifier and amplifier for each channel, and an analog display device such as a CRT monitor, a multi-pen strip recorder or printer. The display is of a wavy line for each channel, showing the patient's brain waves as detected at each electrode.
In addition, more complex and expensive EEG instruments are available and are generally located in hospitals or specialized neurological clinics. These instruments may use more channels, for example, from 19 to 25 channels. They may convert the analog brain wave signals into digital data, analyze the digital data using a data base of normal and abnormal patients, and may produce a topographical map showing the brain and distinguishing normal/abnormal regions by color. Increasing evidence attests to the utility of computerized quantitative analysis of the EEG (QEEG) for early detection and diagnosis of subtle brain dysfunctions. An example of such instruments is the "Spectrum 32" (Cadwell Laboratories) and see U.S. Pat. No. 4,279,258, incorporated by reference herein.
The use of EKG (electrocardiogram) instruments by physicians is much more widespread. An internist, family practitioner or general physician will usually have an EKG instrument in his/her office. Such instruments generally have 3 to 12 channels and consist of a set of electrodes, attachable at the patient's skin near the heart using a conductive gel, an amplifier for each channel, and an analog display device such as a multi-pen recorder.
It is conventional in a physical examination, for example, an annual medical check-up, for the physician to test the patient's heart using the office EKG instrument. However, routine EEG examinations are not given because most physicians do not have an EEG instrument or the training to interpret an EEG analog recording. Even in those instances where EEG screening would be particularly useful, for example, to test school-age children for attention deficit disorder or an elderly person for cerebral ischemia, such mass screening examination is not carried out due to cost, the lack of suitable EEG instruments, the lack of personnel trained to interpret the analog recordings, and the necessity for computer-assisted quantitative analysis as an adjunct to proper interpretation.